P1177 intermitent drop in rpm

[kbomb2788]

Evening. Got one that is kicking my butt....I have a 12 F350 Chassis cab with 190XXX miles on it. While driving at times the vehicle would buck/jerk (some times do it WOT, some times do it moderate throttle). Some times it would set P1177 Code (never did it on my but had it when first got vehicle and when it came back). I tried different combinations of pids and only one that shows fault is "sync" for about 2 movements of forward error it would say "NO". RPM pid never drops (like when cam sensor goes bad and it has a heartbeat graph) and cant find anyother pids that would indicate a problem (saw a GSB about 3 different v ref on 6.7l but could find problem with it. What I have done is change the crank sensor and replaced pig tail and overplayed Crank wiring all the way to pcm. I am at loss and any guidance would be appricieated. Also it does have oil leak out of rear main. also visually checked thrust bearing play and ok. Thank you ahead of time

[tonybullitt]

Is the truck stock or modified? Either way I would pay close attention to the dpf pressure sensor and wiring. If you follow the gsb I am pretty sure the dpf pressure shares vref with crank and cam sensors. 

[cbriggs]

I've had a bunch of vref shorts in the harness to the rear. Also the ebp wiring rubbing through on the firewall insulation above the engine. Gave a symptom a lot like yours actually.

[2006]

I  looked up a P1177, can't find it???

Try disconnecting the throttle plate connector or monitoring the pids for it.

I  had one that the vref wire was broken at the throttle plate connector. Was making a intermittent connection. Was bucking and jerking at various times.

[kbomb2788]

Thank for replay. on P1177

Synchronization

Description This DTC sets when there is an intermittent loss of camshaft to crankshaft synchronization for at least 5 or more occurrences with the engine running. Possible Causes Damaged crankshaft position (CKP) sensor Damaged ignition pulse crankshaft sensor ring Damaged camshaft position (CMP) sensor Damaged CMP sensor target wheel Damaged PCM This is thing is so intermittent... on 4 mile drive it did it twice. I tried to wiggle test around the DPF pressure sensor, Have fan off and tried to wiggle on cam sensor and connector. Tried to mess with throttle plate wiring and other 3 wire sensors I could reach. still nothing. Im about to do the water test (spray with water see if something acts up)

[Keith Browning]

Did you ever resolve this one?

 

[kbomb2788]

I overlayed ckp wire  replaced sensor and tone ring. Customer starts still does it but not as much... If it was warranty I would have replaced engine harness... But there are 5 harness that vref runs through